A catalyst for high density polyethylene film production and a method for preparing the same

Abstract

The application discloses a catalyst for high-density polyethylene film production and a preparation method thereof, and belongs to the technical field of olefin polymerization catalysts. The catalyst takes active magnesium chloride as a carrier, loads titanium tetrachloride active components, and adopts a specific complex internal electron donor system. (1) Tetrahydrofuran and cyclohexanone are added as pre-coordination regulators during the preparation of magnesium chloride alcohol compound; (2) the alcohol compound is dispersed in titanium tetrachloride by means of atomization spraying for low-temperature titanium loading; (3) specific combined siloxane compounds and aromatic carboxylic acid esters are added in stages during the gradient temperature rising process, and ethyl benzoate is added in batches; (4) selective passivation washing is carried out by using a toluene solution containing ethyl acetate in the washing stage. Through the synergistic effect of the four steps, the generation of super-high-activity Ti 3+ centers is selectively inhibited, and the number of polymer "fish eye" defects is greatly reduced.

Description

Technical Field

[0001] This application belongs to the field of olefin polymerization catalyst technology, specifically relating to a catalyst for the production of high-density polyethylene film and its preparation method. Background Technology

[0002] High-density polyethylene (HDPE) film is one of the core raw materials for the packaging industry, with global annual consumption exceeding 35 million tons. Industrially, it is mainly produced using slurry loop polymerization or gas-phase fluidized bed polymerization processes, with Ziegler-Natta catalysts as the core technology. Existing industrial catalysts typically use activated magnesium chloride as a support, loading titanium tetrachloride as the active component, and combining it with internal electron donors such as siloxane compounds and aromatic carboxylic acid esters, which are then activated with alkyl aluminum before being used in ethylene polymerization.

[0003] However, existing catalysts commonly suffer from "fisheye" defects when producing HDPE films. "Fisheyes" are translucent, granular protrusions on the film surface, chemically derived from ultra-high molecular weight polyethylene fractions (molecular weight > 1 million g / mol) dispersed within the polymer. These fractions cannot be fully plasticized at processing temperatures due to excessively high melt viscosity. From the perspective of catalytic chemistry principles, this defect originates from a special type of Ti in the catalyst. 3+ Active center – type ITi with coordination unsaturation and ultra-high chain growth capacity 3+ The center is insensitive to hydrogen chain transfer reactions and tends to continuously insert ethylene molecules, producing ultra-high molecular weight polymers.

[0004] Existing solutions mainly include: using comonomers to adjust the molecular chain structure (high cost, limited selective inhibition effect), bimodal molecular weight distribution process (large equipment investment, difficult process control), optimizing titanium loading (sacrificial activity), and metallocene catalysts (extremely high cost, poor processing performance). Summary of the Invention

[0005] The existing Ziegler-Natta catalyst, when used in the production of HDPE film, suffers from "fish-eye" defects due to the excessively high proportion of ITi³⁺ type active centers (coordinatively unsaturated, with ultra-high chain growth capacity). This invention provides a catalyst for the production of high-density polyethylene film and its preparation method, which significantly reduces "fish-eye" defects while maintaining catalyst activity.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a catalyst for the production of high-density polyethylene film material, comprising the following steps:

[0008] (a) A pre-coordination regulator is added during the preparation of magnesium chloride alcohols from magnesium chloride, wherein the pre-coordination regulator is a mixture of tetrahydrofuran and cyclohexanone;

[0009] (b) The alcohol obtained in step (a) is dispersed in titanium tetrachloride cold liquid at -20 to 0°C by atomized spraying for 0.5 to 1.5 hours;

[0010] (c) The temperature is gradually increased at a rate of 0.2 to 0.8 °C / min, and a first complex electron donor is added in the temperature range of 60 to 85 °C. The first complex electron donor is composed of methylcyclohexyldimethoxysilane, tetramethoxysilane and diisobutyl phthalate. Ethyl benzoate is added in 2 to 4 batches in the temperature range of 90 to 110 °C. The total reaction time is 2 to 5 hours.

[0011] (d) The product obtained in step (c) is subjected to a second titanium tetrachloride loading strengthening treatment, with toluene used for depolymerization in between;

[0012] (e) Wash with toluene 2 to 4 times, with at least one wash using a toluene solution containing ethyl acetate; the toluene solution containing ethyl acetate has a mass concentration of 0.2% to 0.4%.

[0013] (f) Vacuum drying yields the catalyst product.

[0014] Furthermore, in step (a), the mass ratio of tetrahydrofuran to cyclohexanone is 1:0.5 to 1:1.0, the amount of tetrahydrofuran added is 8% to 15% of the mass of magnesium chloride, and the amount of cyclohexanone added is 5% to 10% of the mass of magnesium chloride.

[0015] Furthermore, in step (b), the droplet diameter of the atomized spray is 50–200 μm, the atomization spray rate is 50–80 mL / min, and the volume ratio of titanium tetrachloride to the alcohol is 3:1–4:1.

[0016] Furthermore, in step (c), the first composite electron donor is composed of methylcyclohexyldimethoxysilane, tetramethoxysilane, and diisobutyl phthalate, with addition amounts of 1.0%–1.5%, 0.8%–1.2%, and 0.5%–0.8% of the mass of anhydrous magnesium chloride, respectively.

[0017] Furthermore, in step (c), the total amount of ethyl benzoate added is 1.0% to 2.0% of the mass of magnesium chloride, added in 2 to 4 batches, with the same amount added each time, and the temperature interval between two adjacent additions is 3 to 6°C.

[0018] Furthermore, the secondary titanium tetrachloride loading enhancement treatment in step (d) includes: the first loading reaction at 110-115℃ for 1.5 hours, cooling to 50℃, adding toluene and stirring for 30 minutes for depolymerization treatment, filtering, and then the second loading reaction at 110-120℃ for 1 hour.

[0019] Furthermore, in the secondary titanium tetrachloride loading enhancement treatment described in step (d): during the first loading, the volume mass ratio of titanium tetrachloride to magnesium chloride in step (1) is 3-4 mL / g; during the second loading, the volume mass ratio of titanium tetrachloride to magnesium chloride in step (1) is 2-3 mL / g.

[0020] Furthermore, in step (e), the washing temperature of the toluene solution containing ethyl acetate is 90–95°C, and the washing time is 30 minutes; after washing with ethyl acetate, the solution is washed four times with hexane at a temperature of 40–55°C.

[0021] Specifically, it includes the following sequential steps:

[0022] (1) Under an inert atmosphere, anhydrous magnesium chloride, isooctanol, decane, tetrahydrofuran (THF) and cyclohexanone are mixed, heated to 120-130℃ and reacted for 3-5 hours. The mixture is then cooled to below 70℃ and anhydrous ethanol is added. The mixture is stirred at a constant temperature for 2-4 hours to obtain an alcoholic solution. The mass ratio of magnesium chloride to isooctanol is 1:2.2-1:2.8, the mass ratio of magnesium chloride to decane is 1:4.5-1:5.5, the mass ratio of magnesium chloride to anhydrous ethanol is 1:0.3-1:0.5, the mass ratio of tetrahydrofuran to cyclohexanone is 1:0.5-1:1.0, the amount of tetrahydrofuran added is 8%-15% of the mass of magnesium chloride, and the amount of cyclohexanone added is 5%-10% of the mass of magnesium chloride.

[0023] (2) The alcohol solution obtained in step (1) is sprayed into titanium tetrachloride at a rate of 50-80 mL / min through an atomizing spray device. The diameter of the atomized droplets is 50-200 μm. At the same time, it is dispersed at a high speed of 1000-1500 rpm and the temperature is maintained at -20-0℃ for 0.5-1.5 hours.

[0024] (3) Heat to 60-80°C at a rate of 0.3-0.6°C / min, add the first complex electron donor, and react at a constant temperature for 0.5-1.5 hours; the first complex electron donor is composed of methylcyclohexyldimethoxysilane, tetramethoxysilane and diisobutyl phthalate, and the amounts added are 1.0%-1.5%, 0.8%-1.2% and 0.5%-0.8% of the mass of anhydrous magnesium chloride, respectively;

[0025] (4) Continue to heat to 90-110℃ at a rate of 0.2-0.5℃ / min. During the heating process, add ethyl benzoate in 2-4 batches. The amount added in each batch is 0.25%-0.5% of the mass of magnesium chloride. The temperature interval between two adjacent additions is 3-6℃. After the addition is completed, react at a constant temperature of 105-110℃ for 1.5-2 hours.

[0026] (5) Filter while hot at 105-110℃ and collect the filter cake;

[0027] (6) Add fresh titanium tetrachloride to the filter cake obtained in step (5), the volume mass ratio of titanium tetrachloride to the initial magnesium chloride in step (1) is 3-4 mL / g, heat to 110-115℃ and react for 1.5 hours, cool to 50℃, add toluene and stir for 30 minutes, and filter; add fresh titanium tetrachloride again, the volume mass ratio of titanium tetrachloride to the initial magnesium chloride in step (1) is 2-3 mL / g, heat to 110-120℃ and react for 1 hour, and filter while hot;

[0028] (7) Wash the filter cake obtained in step (6) twice with toluene at 90-100°C, then wash it once with a toluene solution containing 0.2%-0.4% ethyl acetate at 90-95°C, and finally wash it four times with hexane at 40-55°C.

[0029] (8) The filter cake obtained in step (7) is dried at 65-75°C and vacuum of 0.07-0.08 MPa for 5-6 hours to obtain the catalyst product.

[0030] Secondly, the present invention provides a catalyst for the production of high-density polyethylene film material, which is prepared by the above method.

[0031] The catalyst has a titanium content of 4.5%–6.0%, a magnesium content of 15.0%–17.0%, a chlorine content of 60.0%–68.0%, a total internal electron donor content of 4.0%–8.0%, a particle size D50 of 4–6 μm, a particle size distribution width (D90-D10) / D50 ≤ 1.2, and a bulk density ≥ 0.32 g / cm³. 3 .

[0032] Compared with the prior art, the catalyst and its preparation method for producing high-density polyethylene film provided by the present invention have the following beneficial effects:

[0033] The catalyst of this invention controls the catalyst particle size and Ti loading through pre-coordination with THF and cyclohexanone, and loads Ti by low-temperature atomization. 4+ To avoid multi-core Ti caused by local overload 3+ Cluster formation was achieved by adding ethyl benzoate in batches, thus avoiding the Ti-related problems caused by excessive ethyl benzoate. 3+Excessive reduction; adding an appropriate concentration of ethyl acetate and coherently unsaturated Ti during washing. 3+ Reversible coordination occurs, passivating the ultra-high activity type ITi. 3+ The center, while for the normally active type IITi 3+ (i.e., coordination saturation, relatively complete coordination environment, moderate chain growth rate, sensitivity to hydrogen, and generation of medium molecular weight fractions) has little impact. Through four synergistic steps, it significantly reduces polymer "fisheye" defects and improves film quality while maintaining high catalytic activity. Attached Figure Description

[0034] Figure 1 : Schematic diagram of the catalyst preparation process of this invention.

[0035] Figure 2 Particle size distribution curve of catalyst in Example 1.

[0036] Figure 3 Effect of different THF / cyclohexanone mass ratios on catalyst particle size D50 and Ti content.

[0037] Figure 4 Graph showing the relationship between the number of times ethyl benzoate is added and the number of polymer "fish eyes".

[0038] Figure 5 Effect curves of ethyl acetate washing concentration on catalyst activity and "fisheye" number. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only for explaining the invention and not for limiting it. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0041] Test Method Description

[0042] (1) "Fish eye" count test: The polyethylene powder obtained by polymerization was blown into a film with a thickness of 50±5μm at 190℃ and a blow ratio of 2.5. The number of semi-transparent particles with a diameter of 0.3mm or more was counted under a transmission light stage using an optical counter (accuracy 0.1mm). The measurement area was 100cm², and the average value of 3 different positions was taken.

[0043] (2) Catalyst activity test: 1L of n-hexane, 1mmol of triethylaluminum (Al / Ti=50) and appropriate amount of catalyst were added to a 2L stainless steel high-pressure reactor. The temperature was raised to 80℃, and ethylene was introduced to maintain a total pressure of 1.0MPa. Polymerization was carried out for 2 hours, and the activity was calculated by weighing.

[0044] (3) Particle size distribution: laser particle size analyzer, hexane dispersion.

[0045] (4) Ti / Mg content: determined by ICP-OES.

[0046] Example 1

[0047] A catalyst for the production of high-density polyethylene film materials (such as...) Figure 1 ), including the following steps:

[0048] (1) Under N2 protection, add 100g of anhydrous magnesium chloride, 250g of isooctanol, 500g of decane, 10g of THF, and 8g of cyclohexanone (THF / cyclohexanone mass ratio = 1:0.8) to the reactor. Increase the temperature to 125℃ at 1.5℃ / min and stir for 4h until completely dissolved. Cool down to 60℃, add 40g of anhydrous ethanol, and maintain the temperature for 3h. Cool down to 50℃ and set aside.

[0049] (2) Pre-cool 2L of titanium tetrachloride to -15℃. Spray the alcohol solution from step (1) into the solution at 60mL / min (droplet diameter 100μm) while dispersing at 1200rpm and keeping the reaction at -15℃ for 1h.

[0050] (3) Increase the temperature to 70℃ at 0.5℃ / min, add 1.2g of methylcyclohexyldimethoxysilane, 1.0g of tetramethoxysilane, and 0.6g of diisobutyl phthalate, and hold at the temperature for 1h. Increase the temperature to 100℃ at 0.3℃ / min, and add ethyl benzoate (0.4g each time, for a total of 1.2g) in three portions at 90℃, 95℃, and 100℃. Hold at 100℃ for 0.5h, and then continue to increase the temperature to 108℃ and hold at the temperature for 1.5h.

[0051] (4) Filter while hot, add 350 mL of fresh titanium tetrachloride to the filter cake, heat to 112℃ and react for 1.5 h, cool to 50℃, add 80 mL of toluene and stir for 30 min, then filter. Add another 250 mL of titanium tetrachloride, heat to 115℃ and react for 1 h, then filter while hot.

[0052] (5) Wash twice with toluene (95℃) (400 mL each time, 30 min); wash once with toluene solution containing 0.3% ethyl acetate (90℃) (400 mL each time, 30 min); wash twice with n-hexane (50℃) and twice with isohexane (40℃) (300 mL each time, 20 min).

[0053] (6) 70℃, 0.08MPa, N2 purging 0.8m 3 The catalyst was obtained by drying for 5.5 hours at a constant speed.

[0054] Catalyst characterization: Ti=5.22wt%, Mg=15.62wt%, Cl=63.8wt%, total internal electron donor content 6.2%, bulk density 0.34g / cm³.

[0055] The particle size distribution curve of the catalyst prepared in Example 1 is shown below. Figure 2 As shown. From Figure 2 As can be seen, the catalyst particles exhibit a narrow, unimodal distribution morphology, with D50 of 5.22 μm, D10 of 3.86 μm, and D90 of 6.48 μm. The particle size distribution width coefficient (D90-D10) / D50 is 0.50. This particle size distribution characteristic indicates that the catalyst particles have good sphericity and excellent dispersibility, without large particle tails or fine powder shoulders, which is beneficial for maintaining stable polymerization kinetics in the polymerization reactor.

[0056] Polymerization evaluation: Activity 28600gPE / gcat, film "fisheye" count 3 / 100cm 2 .

[0057] To determine the optimal ratio of the pre-coordination regulator tetrahydrofuran (THF) to cyclohexanone, the total amount of THF + cyclohexanone added was fixed at 18% of the mass of anhydrous magnesium chloride. Only the ratio of the two was varied, and the particle size D50 (related to mass and heat transfer in slurry polymerization) and titanium content (related to catalyst activity) of the catalyst were tested. The results are as follows: Figure 3 As shown. From Figure 3 As can be seen, THF and cyclohexanone must be used in combination, and their mass ratio must be strictly controlled between 1:0.5 and 1:1.0. Within this range, the catalyst particle size D50 can be controlled between 4 and 6 μm (facilitating mass and heat transfer in slurry polymerization), and the titanium content should be maintained between 4.5% and 6.0% (corresponding to an activity ≥27000 gPE / gcat). Deviating from this range: pure THF results in excessively large particle size (>8 μm) and wide distribution; excessive cyclohexanone results in excessively low activity.

[0058] The effect of the number of ethyl benzoate (EB) additions on the number of "fish-eye" defects was investigated (the total amount of ethyl benzoate added was fixed at 1.5% of the mass of anhydrous magnesium chloride (approximately 1.2 g / 100 g MgCl2). Other preparation conditions were completely consistent with those in Example 1 (THF / cyclohexanone ratio, temperature program, washing conditions, etc.). Polymerization evaluation conditions were the same: slurry polymerization, 80 °C, 1 MPa ethylene, Al / Ti = 50). The results are as follows: Figure 4 As shown. By Figure 4It can be seen that, with the total amount of ethyl benzoate added remaining constant, the number of additions significantly affects the number of "fish-eye" defects. The optimal number of additions is 2 to 4, with 3 to 4 additions yielding the best results (fish-eye ≤ 5 / 100cm). 2 ).

[0059] The effect of varying ethyl acetate concentration on catalyst activity and the number of "fish eyes" was investigated. The results are as follows: Figure 5 As shown. From Figure 5 As can be seen from this, in order to simultaneously ensure high activity (≥27000gPE / gcat) and low fisheye count (≤5 / 100cm) 2 The ethyl acetate washing concentration should be strictly controlled within the range of 0.2% to 0.4%, preferably 0.3%.

[0060] Example 2

[0061] Difference from Example 1: 12g THF, 10g cyclohexanone (mass ratio 1:0.83), the rest are the same.

[0062] Catalyst: Ti=4.98wt%, D50=4.89μm, activity 27300gPE / gcat, "fisheye" count 2 / 100cm 2 .

[0063] Example 3

[0064] The difference from Example 1 is that ethyl benzoate was added in four separate additions (0.3g each at 85°C, 92°C, 98°C, and 105°C, for a total of 1.2g), while the rest of the additions were the same.

[0065] Catalyst: Ti=5.52wt%, D50=5.31μm, activity 29800gPE / gcat, "fisheye" count 4 / 100cm 2 .

[0066] Comparative Example 1

[0067] Difference from Example 1: THF and cyclohexanone are not added in step (1).

[0068] Catalyst: Ti=6.21wt%, D50=7.65μm, activity 31200gPE / gcat, "fisheye" count 28 / 100cm 2 .

[0069] Comparative Example 2

[0070] The difference from Example 1 is that in step (4), 1.2g of ethyl benzoate is added all at once when the temperature is raised to 90°C, without batches.

[0071] Catalyst: Ti = 5.68 wt%, D50 = 5.42 μm, activity 30100 g PE / gcat, "fish eye" count 18 / 100 cm 2 .

[0072] Comparative Example 3

[0073] The difference from Example 1 is that in step (5), the toluene does not contain ethyl acetate and is washed three times, while the toluene containing ethyl acetate is not used for washing.

[0074] Catalyst: Ti=5.42wt%, D50=5.08μm, activity 29500gPE / gcat, "fisheye" count 16 / 100cm 2 .

[0075] Comparative Example 4

[0076] Difference from Example 1: In step (1), there is 18g of THF and 0g of cyclohexanone.

[0077] Catalyst: Ti = 6.05 wt%, D50 = 8.50 μm, activity 30500 g PE / g cat, "fish eye" count 22 / 100 cm 2 .

[0078] Comparative Example 5

[0079] Difference from Example 1: In step (1), THF 0g and cyclohexanone 18g are used.

[0080] Catalyst: Ti=3.85wt%, D50=4.52μm, activity 18900gPE / gcat, "fisheye" count 12 / 100cm 2 .

[0081] Based on the catalyst activity and "fisheye" results of the above examples and comparative examples, it can be seen that the catalyst of the present invention reduces the number of "fisheyes" to ≤5 / 100cm while maintaining industrially usable activity (≥27000gPE / gcat). 2 This is significantly superior to existing technologies. Comparative Examples 4 and 5 show that THF and cyclohexanone must be combined and the ratio must be within the optimized range; Comparative Examples 2 and 3 show that batch-by-batch addition of EB and washing with ethyl acetate are both necessary steps.

[0082] The catalyst of this invention is used in the production of HDPE film material, which can significantly reduce fisheye defects and improve film quality. It is suitable for high-end application fields such as packaging film, heavy packaging film, and geomembrane.

[0083] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a catalyst for the production of high-density polyethylene film material, characterized in that, Includes the following steps: (a) A pre-coordination regulator is added during the preparation of magnesium chloride alcohols from magnesium chloride, wherein the pre-coordination regulator is a mixture of tetrahydrofuran and cyclohexanone; (b) The alcohol obtained in step (a) is dispersed in titanium tetrachloride cold liquid at -20 to 0°C by atomized spraying for 0.5 to 1.5 hours; (c) The temperature is gradually increased at a rate of 0.2 to 0.8 °C / min, and a first complex electron donor is added in the temperature range of 60 to 85 °C. The first complex electron donor is composed of methylcyclohexyldimethoxysilane, tetramethoxysilane and diisobutyl phthalate. Ethyl benzoate is added in 2 to 4 batches in the temperature range of 90 to 110 °C. The total reaction time is 2 to 5 hours. (d) The product obtained in step (c) is subjected to a second titanium tetrachloride loading strengthening treatment, with toluene used for depolymerization in between; (e) Wash with toluene 2 to 4 times, with at least one wash using a toluene solution containing ethyl acetate; the toluene solution containing ethyl acetate has a mass concentration of 0.2% to 0.4%. (f) Vacuum drying yields the catalyst product.

2. The method for preparing a catalyst for the production of high-density polyethylene film material according to claim 1, characterized in that, The mass ratio of tetrahydrofuran to cyclohexanone in step (a) is 1:0.5 to 1:1.0, the amount of tetrahydrofuran added is 8% to 15% of the mass of magnesium chloride, and the amount of cyclohexanone added is 5% to 10% of the mass of magnesium chloride.

3. The method for preparing a catalyst for the production of high-density polyethylene film material according to claim 1, characterized in that, In step (b), the droplet diameter of the atomized spray is 50-200 μm, the atomization spray rate is 50-80 mL / min, and the volume ratio of titanium tetrachloride to magnesium chloride alcohol is 3:1-4:

1.

4. The method for preparing a catalyst for the production of high-density polyethylene film material according to claim 1, characterized in that, In step (c), the first complex electron donor is composed of methylcyclohexyldimethoxysilane, tetramethoxysilane and diisobutyl phthalate, and the amounts added are 1.0% to 1.5%, 0.8% to 1.2% and 0.5% to 0.8% of the mass of magnesium chloride, respectively.

5. The method for preparing a catalyst for the production of high-density polyethylene film material according to claim 1, characterized in that, In step (c), the total amount of ethyl benzoate added is 1.0% to 2.0% of the mass of magnesium chloride, added in 2 to 4 batches, with the same amount added each time, and the temperature interval between two adjacent additions is 3 to 6°C.

6. The method for preparing a catalyst for the production of high-density polyethylene film material according to claim 1, characterized in that, The secondary titanium tetrachloride loading enhancement treatment in step (d) includes: the first loading reaction at 110-115℃ for 1.5 hours, cooling to 50℃, adding toluene and stirring for 30 minutes for depolymerization treatment, filtering, and then the second loading reaction at 110-120℃ for 1 hour.

7. The method for preparing a catalyst for the production of high-density polyethylene film material according to claim 6, characterized in that, In the secondary titanium tetrachloride loading enhancement treatment described in step (d): during the first loading, the volume-to-mass ratio of titanium tetrachloride to magnesium chloride in step (a) is 3-4 mL / g; during the second loading, the volume-to-mass ratio of titanium tetrachloride to magnesium chloride in step (a) is 2-3 mL / g.

8. The method for preparing a catalyst for the production of high-density polyethylene film material according to claim 1, characterized in that, The washing temperature of the toluene solution containing ethyl acetate in step (e) is 90-95°C, and the washing time is 30 minutes; after washing with ethyl acetate, the solution is washed four times with hexane at a temperature of 40-55°C.

9. A method for preparing a catalyst for the production of high-density polyethylene film material, characterized in that, Prepared by the method described in any one of claims 1-8.

10. A catalyst for the production of high-density polyethylene film material according to claim 9, characterized in that, The catalyst has a titanium content of 4.5%–6.0%, a magnesium content of 15.0%–17.0%, a chlorine content of 60.0%–68.0%, a total internal electron donor content of 4.0%–8.0%, a particle size D50 of 4–6 μm, a particle size distribution width (D90-D10) / D50 ≤ 1.2, and a bulk density ≥ 0.32 g / cm³. 3 .

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